Choking Engine?

Recently the hangers for my exhaust system broke, leaving my system on the ground. I have repaired the hangers and now after the car warms up I will experience a loss of power.

During driving it will unexpectedly lose power and sounds as if it is choking. The RPMs drop and there does not appear to be a transmission problem. Sometimes turning the car off will eliminate the problem, other times it is ineffective.

I have checked (and have had checked with a MB certified mechanic {who said it should not be doing this});

Engine (#3 cylinder not firing)
Exhaust (no damage seen, catalytic converter intact inside and out)
Air filter
Fuel filter & pump
Wiring
Transmission

At a loss here, do not know where the issue is coming from. Going from 60mph to 20 mph on the highway is dangerous. This is my only form of transport and I need help!

Thanks in advance!